1. Developing a Technical Guide for Water Sensitive Urban Design Wellington Water
16 March 2017

2. Overview Background and project drivers
Water sensitive urban design and Wellington examples
Whaitua and NPS freshwater
Existing NZ approaches to WSUD design
Our proposed approach
Other approaches
Conclusion and questions

3. 5 of the 9 councils have centralised 3 waters with Wellington Water
Where we work
5 of the 9 councils have centralised 3 waters with Wellington Water

4. Project Drivers Lift WSUD design standards in Wellington
Avoid expensive failures
Make it easier for developers to use WSUD approaches
Building block for addressing water quality issues
Promote WSUD (Environmental, Economic, Aesthetic, Education)

5. What is water sensitive urban design?

6. Wellington Area WSUDs

7. Examples

8. Legal Background and Whaitua
Proposed Natural Resources Plan was notified in July 2015
PNRP hearings will start in April
5 Whaitua identified for the region
Porirua Whaitua in full swing
Wellington Whaitua (including Hutt Valley) will start in Nov
Whaitua will determine the outcomes we are trying to achieve

9. New Zealand Approaches
Auckland TP10/ TP108
Christchurch guideline
NZTA
Hamilton and Nelson
Most approaches based on USA methods from Maryland and Delaware (Earl Shaver)

10. Current TP10 Design Basis
1/3 of a 2 year event =
capture of 80% of all runoff on long-term runoff volume
capture of 80% of all runoff on long-term runoff volume
= remove 75% SS
Guo and Urbonas 1996
Urbonas et al 1990

11. Current TP10 Design Basis
Analysis of TP10 design basis for Auckland Unitary Plan:

12. Current TP10 Design Basis
Analysis of TP10 design basis for Auckland Unitary Plan:

13. Our Current Thoughts Rainfall depth that 90% of storms are less than
Device Performance
(Area based eg Wetlands)
Hydrological Analysis
Ratio of treatment device to effective impervious areas
Device Performance
(Area based g Raingardens)
Rainfall intensity that 90% of storms are less than

14. Initial Steps One workshop with interested consultants held
Second workshop with wider teams proposed

15. Contaminants of Concern
Likely to include SS, Zn, Cu and possibly TN in Porirua; TP in streams
Melbourne Approach:
Also Get:
80% SS
Zn, Cu
45% TN
Microbiological
45% TP

16. Conclusions
We have an opportunity to lift the standard of WSUD in Wellington
We will be drawing from other NZ approaches, but probably with some twists
Likely to be more that Suspended Solids
We think there is an opportunity to go smaller but focus on the quality of construction and maintenance